From 2454b5449bbda815eb15327476e376d0d3a39617 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Wed, 5 Mar 2025 22:16:56 +0000
Subject: Move camera out of gl folder, it's not OpenGL specific

---
 gfx/camera.cpp | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 gfx/camera.cpp

(limited to 'gfx/camera.cpp')

diff --git a/gfx/camera.cpp b/gfx/camera.cpp
new file mode 100644
index 0000000..9e165fa
--- /dev/null
+++ b/gfx/camera.cpp
@@ -0,0 +1,67 @@
+#include "camera.h"
+#include <collections.h>
+#include <glm/gtx/transform.hpp>
+#include <maths.h>
+#include <ray.h>
+
+Camera::Camera(GlobalPosition3D pos, Angle fov, Angle aspect, GlobalDistance zNear, GlobalDistance zFar) :
+	position {pos}, forward {::north}, up {::up}, near {zNear}, far {zFar}, view {},
+	projection {
+			glm::perspective(fov, aspect, static_cast<RelativeDistance>(zNear), static_cast<RelativeDistance>(zFar))},
+	viewProjection {}, inverseViewProjection {}
+{
+	updateView();
+}
+
+Ray<GlobalPosition3D>
+Camera::unProject(const ScreenRelCoord & mouse) const
+{
+	static constexpr const glm::vec4 SCREEN {0, 0, 1, 1};
+	return {
+			.start = position,
+			.direction = glm::normalize(glm::unProject(mouse || 1.F, view, projection, SCREEN)),
+	};
+}
+
+void
+Camera::updateView()
+{
+	view = glm::lookAt({}, forward, up);
+	viewProjection = projection * view;
+	inverseViewProjection = glm::inverse(viewProjection);
+	static constexpr auto PLANES = std::array {0, 1, 2} * std::array {1.F, -1.F};
+	std::ranges::transform(PLANES, frustumPlanes.begin(), [vpt = glm::transpose(viewProjection)](const auto & idxs) {
+		const auto [idx, sgn] = idxs;
+		return vpt[3] + (vpt[idx] * sgn);
+	});
+}
+
+Direction3D
+Camera::upFromForward(const Direction3D & forward)
+{
+	const auto right = crossProduct(forward, ::down);
+	return crossProduct(forward, right);
+}
+
+std::array<GlobalPosition4D, 4>
+Camera::extentsAtDist(const GlobalDistance dist) const
+{
+	const auto clampToSeaFloor = [this, dist](GlobalPosition3D target) -> GlobalPosition4D {
+		target += position;
+		if (target.z < -1500) {
+			const CalcPosition3D diff = target - position;
+			const CalcDistance limit = -1500 - position.z;
+			return {position + ((limit * diff) / diff.z), (limit * dist) / diff.z};
+		}
+		return {target, dist};
+	};
+	const auto depth = -(2.F * (static_cast<float>(dist - near)) * static_cast<float>(far))
+					/ (static_cast<float>(dist) * (static_cast<float>(near - far)))
+			- 1.F;
+	static constexpr const std::array extents {-1.F, 1.F};
+	static constexpr const auto cartesianExtents = extents * extents;
+	return cartesianExtents * [&depth, this, &clampToSeaFloor](const auto & extent) {
+		const glm::vec4 in {extent.first, extent.second, depth, 1.F};
+		return clampToSeaFloor(perspective_divide(inverseViewProjection * in));
+	};
+}
-- 
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